Grinding machine and method of grinding

ABSTRACT

A grinding machine and a method for grinding buttons of a rock drill bit are disclosed. The grinding machine has a frame and a grinding head. The grinding head has a rotatable grinding spindle. The free end of the grinding spindle is intended to drive, and to replaceably carry, a grinding cup. The grinding spindle has a first rotational axis, the grinding spindle being intended to rotate around the same as well as also around a second rotational axis. The first rotational axis of the grinding spindle is arranged to assume at least two separate positions, one of which positions is collinear with the second rotational axis and the second of which positions places the first rotational axis at an angle β with the second rotational axis.

FIELD

The present disclosure relates to a grinding machine and a method for grinding buttons of a rock drill bit according to the preambles of the independent claims.

BACKGROUND

In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.

By, for example, WO/0204169, a grinding machine is previously known for grinding buttons of a rock drill bit, the grinding machine comprising a grinding head having a rotatably mounted spindle, which carries a grinding cup. Upon use of the grinding machine, muscular strength is required for operating the grinding head, which is suspended in a link-lever system. This complicates the design of the grinding machine and decreases the accuracy during grinding. Furthermore, the task is physically heavy for the operator.

SUMMARY

An object of the presently disclosed grinding machine and method is to provide for easy grinding of buttons of rock drill bits, is to provide a grinding machine and a method for obtaining good repetition accuracy upon grinding of buttons of rock drill bits, is to provide a grinding machine and a method for obtaining accurate centering of the grinding cup upon grinding of buttons of rock drill bits, and is to provide a grinding machine and a method for enabling the return to one and the same position after grinding of the respective button of a rock drill bit.

These and other objects have been attained by means of a grinding machine and a method wherein, among other things, a first rotational axis of a grinding spindle is arranged to assume at least two separate positions, one of which positions is collinear with a second rotational axis and/or a button is ground under simultaneous slanting of a grinding cup, from a first position where the first rotational axis of the grinding spindle is collinear with the second rotational axis to a second position where the first rotational axis and the second rotational axis form an angle with each other.

An exemplary grinding machine for grinding a button of a rock drill bit comprises a frame, and a grinding head, the grinding head including a rotatable grinding spindle, wherein a free end of the grinding spindle drives and replaceably carries a grinding cup, wherein the grinding spindle has a first rotational axis, the grinding spindle rotating around the first rotational axis as well as also around a second axis, and wherein the first rotational axis of the grinding spindle is arranged to assume at least two separate positions, one of which positions is collinear with the second rotational axis.

An additional exemplary embodiment of a grinding machine for grinding a button of a rock drill bit comprises a frame, a grinding head, the grinding head including a rotatable grinding spindle and a grinding cup at a first end, and a positioning unit operatively connected to the grinding head at a second end of the grinding head, wherein the grinding head and positioning unit are operatively connected to the frame to translate the grinding head and positioning unit axially along a first axis, and wherein the second end of the grinding head is displaceable relative to the positioning unit within an area that is defined by a spherical cone.

Another exemplary grinding machine for grinding a button of a rock drill bit comprises a frame, a grinding head, the grinding head including a rotatable grinding spindle and a grinding cup at a first end, and a positioning unit operatively connected to the grinding head at a second end of the grinding head, wherein the grinding head and positioning unit are operatively connected to the frame to translate the grinding head and positioning unit axially along a first axis, wherein the second end of the grinding head is displaceable relative to the positioning unit, and wherein the grinding head is operative over a continuum of positions from a first position in which a rotational axis of the grinding head is coincident with the first axis to a second position in which the rotational axis forms an angle with the first axis.

An exemplary method for grinding the buttons of a rock drill bit by means of a grinding machine, wherein the grinding machine includes a frame and a grinding head, the grinding head including a rotatable grinding spindle, a free end of the grinding spindle driving and replaceably carrying a grinding cup, the grinding spindle having a first rotational axis, the grinding spindle rotatable around the first rotational axis as well as also around a second rotational axis, comprises at least the following steps: positioning the grinding cup in a starting position so that the first rotational axis of the grinding spindle substantially coincides with a centre axis of the button that is to be ground, starting rotation of the grinding spindle around the first rotational axis and around the second rotational axis, feeding the grinding cup toward the button until the grinding cup abuts against the button, grinding the button under simultaneous slanting of the grinding cup, from a first position where the first rotational axis of the grinding spindle is collinear with the second rotational axis to a second position where the first rotational axis and the second rotational axis form an angle with each other, and after a certain time of grinding, guiding the grinding cup back to the starting position.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWING

The following detailed description can be read in connection with the accompanying drawings in which like numerals designate like elements and in which:

FIG. 1 shows parts of a grinding machine according to the present invention in side view in a first position in connection with grinding of a rock drill bit.

FIG. 2 shows parts of the grinding machine in side view in a second position.

FIG. 3 schematically shows within which area parts of the grinding machine can move.

DETAILED DESCRIPTION

As is seen in FIGS. 1 and 2, an exemplary embodiment of a grinding machine comprises a grinding head 10, which comprises a driving source 12, preferably an electric motor. Alternatively, the driving source may be arranged outside the grinding head. The grinding head 10 can be displaced vertically in relation to a frame 11, i.e., downward and upward, by means of an arrangement, not shown. The frame 11 is intended to constitute a stand for holding and guiding the grinding head. The grinding head in FIGS. 1 and 2 comprises the driving source 12 along the longitudinal axis of which a rotatable grinding spindle 13 extends.

The grinding spindle is intended to rotate around a first rotational axis CL1. The free end 14 of the grinding spindle 13 is intended to drive and to replaceably carry a grinding cup 15. The rotary grinding spindle 13 executes, via the grinding cup 15, the grinding of the selected cemented-carbide button 36. The other end 16 of the grinding spindle 13, i.e., the end facing away from the free end 14 of the grinding spindle 13, can assume different positions in relation to a fixed, second rotational axis CL2. The other end 16 is arranged to assume at least two separate positions, one of which positions is intersected by the second rotational axis CL2. This means that at least in some arrangements, the grinding spindle also is intended to rotate around the second rotational axis CL2, so that the first rotational axis CL1 of the grinding spindle is arranged to assume at least two separate positions in relation to the second rotational axis CL2. One of these positions is collinear with the second rotational axis CL2. The other of these positions has the first rotational axis CL1 forming an angle β with the second rotational axis CL2. Here, by “collinear” is meant that the first rotational axis CL1 and the second rotational axis CL2 coincide with each other irrespective of which view they are regarded in. Thus, the other end 16 of the grinding spindle 13 is arranged to assume at least two separate positions, one of which positions is intersected by the second rotational axis CL2.

A rotation unit 17 is rotatably mounted via bearing members 18 to a part 19 of the grinding head 10 that is not rotatable in relation to the frame 11. The part 19 is via a support member 20 vertically adjustably connected to the frame 11. A motor 21 is attached in the support member 20 and coupled to the rotation unit 17 in order to drive the rotation unit 17. The rotation unit 17 comprises a support shaft 22, which extends through the part 19. Said support shaft 22 is intended to rotate around the second rotational axis CL2 when the motor 21 is activated.

The support shaft 22 is fixedly connected to a position indicator member 23. The position indicator member 23 comprises, in the embodiment illustrated, two plane-parallel sheet-metal plates or sides 24, which are connected to each other via an upper sheet-metal plate or side 25. Each side 24 comprises a curved groove 26, the centre line 27 of which may be described by a radius R having a radius centre C as shown in FIG. 2. Said radius centre coincides substantially with a radius centre of a cavity 28 of the grinding cup 15. The ends 28, 29 of the groove 26 may constitute fixed stops for the slanting of a motor bracket 30. Alternatively, an adjustable stop may be provided near at least one of the ends of the groove 26.

The driving source or the motor 12 is rotatably mounted in the motor bracket 30, for example via a co-operating journal 31 in the motor and bearing members 32, so that the driving source in its entirety can rotate in relation to the motor bracket and the first rotational axis CL1. The above-mentioned journal may alternatively be arranged on an intermediate part, which holds the motor in a way similar to what is shown in the figures.

The motor bracket 30 comprises two pairs of wheels or two pairs of followers 33 intended to be guided by the grooves 26 along a curved path when the motor bracket is actuated by an actuator 34. The actuator 34 is turnably fixed in the position indicator member 23 as well as turnably connected to the motor bracket 30, so that when the length of the actuator is altered, the motor bracket 30 follows the path of the grooves 26. The actuator 34 may, for example, be an air cylinder, an electric motor or the like. The upper portion of the support shaft 22 in the shown embodiment has recesses for receiving connections for air.

When the actuator 34 is extended (FIG. 1), the first rotational axis CL1 and the second rotational axis CL2 can coincide, wherein a starting position has been assumed. When the actuator 34 is contracted (FIG. 2), the same can be arranged substantially perpendicularly to the second rotational axis CL2, wherein a working position has been assumed.

Thus, the position indicator member 23 is arranged to rotate around the second rotational axis CL2. Hence, the position indicator member 23 or the rotation unit 17 comprises members 26, 30, 33 and 34 for adjusting the first rotational axis CL1 of the grinding spindle in relation to the second rotational axis CL2. Thus, the members 26, 33 and 34 for adjusting the first rotational axis CL1 of the grinding spindle in relation to the second rotational axis CL2 are arranged to lock the other end 16 of the grinding spindle in a path, which substantially may be described by a radius R.

The other end 16 of the grinding spindle 13 can be displaced within an area that may be defined by a spherical cone Z, schematically shown in FIG. 3. The spherical cone Z has a cone angle of 10 to 900. For instance, a smaller cone angle is used upon grinding of acute buttons.

As typical values, it may be mentioned that if the spindle 13 rotates by >10000 r/min, the position indicator member 23 rotates by approx. 60-100 r/min.

In some exemplary embodiments, members 35 for supplying flush medium to the grinding spindle 13 are mounted on the part of the grinding spindle 13 that is situated outside the driving source 12.

Exemplary embodiments of the disclosed grinding machine described above operate in the following way. The grinding head 10 is lowered and simultaneously the drill bit 37 is displaced until the recess 28 in the grinding cup 15 is correctly orientated in relation to the button 36 that is to be ground. After that, the drill bit is locked in the position thereof. Position the grinding cup 15 in a starting position so that the first rotational axis CL1 of the grinding spindle substantially coincides with the centre axis of the button that is to be ground. Start rotation of the grinding spindle around the first rotational axis CL1 and around the second rotational axis CL2. Feed the grinding cup 15 toward the button until the grinding cup abuts against the button 36 that is to be ground, in accordance with FIG. 1. Grind the button under simultaneous slanting of the grinding cup, from a position where the first rotational axis CL1 of the grinding spindle is collinear with the second rotational axis CL2 to a position where the first rotational axis CL1 and the second rotational axis CL2 form an angle β with each other, for instance 10°, in accordance with FIG. 2. Then, after a certain time of grinding, the grinding cup 15 is guided back to the starting position. It is an advantage to guide the grinding cup so that it returns to the starting position or a standby position where the first rotational axis CL1 and the second rotational axis CL2 become collinear, since the drill bit or the grinding head then can be indexed or moved, respectively, wherein a new button can be ground without any adjustment work needing to be made.

When the driving source 12 starts, simultaneously the supply of flush medium, preferably water, begins and flows to the flushing head 35 and then to mouths in the recess 28 of the grinding cup 15 for providing flushing and cooling of the button that is to be ground.

Thus, the present disclosure relates to grinding machines and methods for easy grinding of buttons of rock drill bits, good repetition accuracy and accurate centering of the grinding cup being obtained.

Although described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims. 

1. A grinding machine for grinding a button of a rock drill bit, the grinding machine comprising: a frame; and a grinding head, the grinding head including a rotatable grinding spindle, wherein a free end of the grinding spindle drives and replaceably carries a grinding cup, wherein the grinding spindle has a first rotational axis, the grinding spindle rotating around the first rotational axis as well as also around a second axis, and wherein the first rotational axis of the grinding spindle is arranged to assume at least two separate positions, one of which positions is collinear with the second rotational axis.
 2. The grinding machine according to claim 1, wherein the end of the grinding spindle facing away from the free end of the grinding spindle is arranged to assume at least two separate positions, one of which positions is intersected by the second rotational axis.
 3. The grinding machine according to claim 1, wherein the end of the grinding spindle facing away from the free end of the grinding spindle can be displaced within an area that is defined by a spherical cone.
 4. The grinding machine according to claim 3, wherein the spherical cone has a cone angle of 1° to 90°.
 5. The grinding machine according to claim 1, wherein a rotation unit, which is rotatably mounted in the frame and carries the grinding spindle, is arranged to rotate around the second axis, the rotation unit comprising members for adjusting the first rotational axis of the grinding spindle in relation to the second rotational axis.
 6. The grinding machine according to claim 5, wherein the members for adjusting the first rotational axis of the grinding spindle in relation to the second rotational axis are arranged to lock the other end of the grinding spindle in a path, which substantially is described by a radius having a radius centre, and in that said radius centre substantially coincides with a radius centre of a cavity of the grinding cup.
 7. The grinding machine according to claim 5, wherein the members for adjusting the first rotational axis of the grinding spindle in relation to the second rotational axis comprise curved grooves arranged in the rotation unit and co-operating with followers arranged on a motor bracket, and in that actuators are arranged to lock the motor bracket in a desired position in relation to the grooves.
 8. The grinding machine according to claim 7, wherein a driving source for the grinding spindle is rotatably mounted in the motor bracket, so that the driving source in its entirety can rotate in relation to the motor bracket and the first rotational axis.
 9. The grinding machine according to claim 1, wherein a member for supplying flush medium to the grinding spindle is mounted on a part-of the grinding spindle that is situated outside a driving source.
 10. The grinding machine according to claim 1, wherein the grinding head is displaceable relative to the frame.
 11. A method for grinding the buttons of a rock drill bit by means of a grinding machine, the grinding machine including a frame; and a grinding head, the grinding head including a rotatable grinding spindle, a free end of the grinding spindle driving and replaceably carrying a grinding cup, the grinding spindle having a first rotational axis, the grinding spindle rotatable around the first rotational axis as well as also around a second rotational axis, the method comprising at least the following steps: positioning the grinding cup in a starting position so that the first rotational axis of the grinding spindle substantially coincides with a centre axis of the button that is to be ground; starting rotation of the grinding spindle around the first rotational axis and around the second rotational axis; feeding the grinding cup toward the button until the grinding cup abuts against the button; grinding the button under simultaneous slanting of the grinding cup, from a first position where the first rotational axis of the grinding spindle is collinear with the second rotational axis to a second position where the first rotational axis and the second rotational axis form an angle with each other; and after a certain time of grinding, guiding the grinding cup back to the starting position.
 12. A grinding machine for grinding a button of a rock drill bit, the grinding machine comprising: a frame; a grinding head, the grinding head including a rotatable grinding spindle and a grinding cup at a first end; and a positioning unit operatively connected to the grinding head at a second end of the grinding head, wherein the grinding head and positioning unit are operatively connected to the frame to translate the grinding head and positioning unit axially along a first axis, and wherein the second end of the grinding head is displaceable relative to the positioning unit within an area that is defined by a spherical cone.
 13. The grinding machine according to claim 12, wherein the spherical cone has a cone angle of 1° to 90°.
 14. The grinding machine of claim 12, wherein a vertex of the cone angle is the first end of the grinding head.
 15. A grinding machine for grinding a button of a rock drill bit, the grinding machine comprising: a frame; a grinding head, the grinding head including a rotatable grinding spindle and a grinding cup at a first end; and a positioning unit operatively connected to the grinding head at a second end of the grinding head, wherein the grinding head and positioning unit are operatively connected to the frame to translate the grinding head and positioning unit axially along a first axis, wherein the second end of the grinding head is displaceable relative to the positioning unit, and wherein the grinding head is operative over a continuum of positions from a first position in which a rotational axis of the grinding head is coincident with the first axis to a second position in which the rotational axis forms an angle with the first axis.
 16. The grinding machine of claim 15, wherein the angle is 1 to 90°. 